Donadon is serving a 13-year prison sentence for corruption. He is the first serving Congressman to be sent to prison since Brazil returned to democracy in the 1980s.

Congressional President Henrique Alves said the vote had been a blow for the credibility of Brazilian lawmakers.

Analysis

By Joao FelletBBC Brasil

The decision was an attempt to counter the criticism the Brazilian Congress has been facing lately. It comes a few days before Brazil's independence day, on 7 September, when protests are set to take place across the country.

Members of Congress are worried that, as during the wave of demonstrations in June, much of the people's anger in the upcoming protests will be directed at the politicians, who are seen by many as ineffective and corrupt.

It seems unlikely that the decision will change public opinion. There are no indications that the Senate will pass the measure abolishing secret ballots anytime soon.

Brazilians' views are still marked by the ongoing Mensalao trial, one of the biggest corruption scandals in the country's recent history, in which several legislators were convicted.

"I can say, without the shadow of a doubt, that I have never seen the credibility of this house take a worse hit than the one last week," he said.

The case of Donadon and other lawmakers convicted of crimes but still serving in Congress was described as a slap in the face by protesters.

Hundreds of thousands of people demonstrated in cities such as Sao Paulo, Rio de Janeiro and Salvador, demanding broad reforms to the education, health care and transport sectors, as well as an end to widespread corruption at all levels of the public sector.

The ability of Congress to hold votes in secret was seen as one of the ways legislators accused of corruption could stay in power, as their colleagues closed ranks without having to face criticism from angry constituents.

The measure will now go to the Senate, where some politicians have been critical of the move, arguing that it will make it harder for them to follow their conscience.